1. Field of Disclosure
The present disclosure relates to a composition having an oil-in-water dispersion with enhanced stability that can be applied into or onto a food or beverage to enhance the physical, chemical, nutritional, and/or sensory properties of the food or beverage, and also to prevent freezer burn. More particularly, the present disclosure relates to a composition having an oil-in-water dispersion with particles of a hydrophobic agent having an average particle size between about 100 to about 999 nm. The distribution of particles are monodispersed about the average particle size, with at least 75 wt % of the particles having a particle size that is ±300 nm of the average particle size. A small negative charge imparted to each of the particles by the mechanical process employed to form the oil-in-water dispersion causes the particles to repel each other, further enhancing stability of the dispersion.
2. Description of Related Art
Conventional techniques for combining a hydrophobic material (such as a liquid, semi-solid, or solid) with a hydrophilic liquid require the addition of agents that change the properties of both the hydrophobic material and the hydrophilic liquids so that they more closely resemble one another. As the properties of the two phases converge because of the additives, they have a greater propensity to be stable for a commercially viable period of time. An important class of additives that can be used in these hydrophobic phase/hydrophilic phase combinations is the surface active agent, which is typically referred to as a “surfactant” which have both hydrophobic and hydrophilic properties.
When one or more of the surface active agents are incorporated into the hydrophobic phase or the hydrophilic phase or both, the surfactants will align themselves at the hydrophobic phase-hydrophilic phase interface or at the interface between the composition and the surrounding air. The force that exists at the hydrophobic phase-hydrophilic phase interface (“Interfacial Tension”) is reduced allowing the two phases to more favorably coexist. Similarly, the force that exists at the air-composition interface (“Surface Tension”) is also reduced. A special sub-category of surfactants is called an emulsifier. When carefully selected, such emulsifiers have a wide range of surface-active properties. These materials not only lower interfacial tension at the hydrophobic phase/hydrophilic phase interface but, with the input of shearing energy, enable the formation of stable droplets of one phase within the other. The resulting product is called an emulsion. In many cases such emulsions are prepared by heating the hydrophobic and hydrophilic phases to a temperature of 70° C. or greater before combining the two phases. The purpose of heating the phases is to ensure that all semi-solid and solid hydrophobic materials used are melted, and that the two phases have a low enough viscosity so the two phases can mix freely. The hydrophobic and hydrophilic phases are mixed together until they achieve a homogeneous appearance. Thereafter, the mixture is cooled to ensure the formation of appropriately sized droplets, usually in the 3 micron to 10 micron range. Such emulsions typically have a homogeneous, opaque, white appearance due to their particle size.
Although surfactants have provided many benefits, the use of surfactants in foods has several disadvantages, including producing emulsions that are thermodynamically unstable, non-reproducible, difficult-to-scale and are potentially unhealthy when consumed.
The time to develop a traditional emulsifier-based product is lengthy. When changes to either the aqueous phase or oil phase are made, for example due to supply issues or changing consumer preferences, the previously effective emulsifier blend generally must be altered. Such changes may undesirably result in a change in one or more aesthetic, performance, or health properties. Immediate stability of the composition is often compromised as a result and, worse, resulting instability may not be identified until the second or third month of accelerated stability testing. This can compromise the long-term shelf life of the product. Correction requires a complex, often empirical, rebalancing of the formulation.
Compounding these production and stability issues are the effects that processing can have on the outcome of a batch. Emulsion stability is dependent on a variety of parameters such as the zeta potential, particle size, crystal formation, and water binding activity of the ingredients employed to achieve the desired rheological properties of the product. These parameters are dependent on the temperature to which the oil and water phases are heated, the rate of heating, the method and rate of mixing of the phases when combined at elevated temperatures, and the rate of cooling. Most emulsions require heating to ensure that all higher melting point materials, such as waxes and butters, are completely melted, dissolved, or dispersed in the appropriate phase or to accelerate the hydration of starches and other thickening agents.
Some emulsions are made without heating but these systems preclude the use of higher melting point materials that can add richness to the oral aesthetics of the final product. Further, if the rate of mixing is high, there is a chance that air can be entrapped in the emulsion. This phenomenon causes an undesirable decrease in the specific gravity of the product and an increase in product viscosity. Any variability in processing can lead to a range of undesirable rheological and textural properties. This issue can occur even if the formulation is not modified. Often, if two or more formulators prepare the same product, the resulting compositions may vary considerably. This surprising variation can occur even though each person utilized the same lots of raw ingredients. The unsettling phenomenon occurs because it may be very difficult to exactly reproduce all of the processing parameters used to make an emulsion. If processing variables vary in small, difficult-to-track ways, unexpected particle size variations may occur, or the crystalline properties of the emulsion can be compromised.
Given these concerns, a typical 500-g to 2000-g lab preparation may not translate directly to a manufacturing environment. Moreover, equipment used in the laboratory generally does not well model that used in the plant. There is usually a need for an intermediate development phase during scale-up that facilitates this transition. Some equipment for this intermediate phase is engineered to mimic plant conditions but at a fraction of the size. Even so, scale-up issues abound. To deal with the vagaries of scale-up, the product may be subjected to a wide range of processing variations in order to optimize the conditions of manufacture. Products made at each level of scale-up are typically subjected to accelerated stability testing to ensure the integrity of the product for its anticipated shelf life. These issues increase the time and cost of bringing a new product into production. As a consequence, most formulators tend to stay with certain tried and true approaches of the past, thereby minimizing uniqueness and ingenuity.
Traditional emulsion systems also create difficulties in manufacturing. The need for heating and cooling systems, specialized mixing equipment, and assorted additional processing devices makes the manufacture of emulsion systems capital intensive. Further, the equipment specifications and energy requirements will vary from country to country. This situation will cause a modification in the processing variables thereby making it almost impossible to have a truly “global” manufacturing protocol. The energy needed to process such products can be costly. Similarly, there is typically a long batch processing time. It can take from 5 to 24 hours, or more, to complete the processing of emulsions depending on the batch size and number of sub-phases required. This reality requires intensive labor that adds to cost.
In the surfactant mediated process, the need for high temperature water or steam to heat the phases of the batch can cause damage to heat sensitive hydrophobic agents. Prolonged heating of certain materials can accelerate the reaction of the hydrophobic agent with other components in the emulsion, or with air. For example, unsaturated hydrocarbons, such as vegetable oils, can oxidize, which lead to rancidity or an undesirable color change. Prolonged heating can reduce the potency of hydrophobic nutritional compounds, such as vitamins and antioxidants, as well as modify flavor-providing molecules. In today's market, consumers are less accepting of non-natural stabilizing agents (such as preservatives, artificial flavors or aromas, chelating agents, and synthetic antioxidants) to address these concerns.
The presence of surfactants, preservatives, chelating agents, and other synthetic additives raises safety and health concerns in consumers. These materials are perceived to be artificial and not natural. Their inclusion creates processed food, which has been linked to obesity, diabetes, carcinogenicity, teratology, arthritis, high blood pressure, arteriosclerosis, and a compromised immune system. Because of these issues there is rising regulatory pressure and pressure from consumer activists to remove such artificial agents from compositions intended for human consumption.
The presence of emulsifiers in food products as well as the super-micron particle size micelles that they form can also result in a sub-optimal taste sensation and limited textural variability creating a less enjoyable eating or drinking experience.
Surfactant micelles, nanospheres, nanoparticles, nanoemulsions, nanocochleates, liposomes, nanoliposomes, and other encapsulating delivery systems have been used to address some of the issues described above. Mozafari, et al. describe the various ways to make liposomes and nano-liposomes, which are closed, continuous, vesicular structures composed mainly of phospholipid bilayer(s) in an aqueous environment (2008, Journal of Liposomal Research 18:309-327). However, these systems contain either a specific bi-layer structure or other encapsulating techniques such as cyclodextrin entrapment or crosslinked polycarbohydrate encapsulate. Further, the surfactant micelles, nanospheres, nanoparticles, and nanoemulsions contain emulsifiers that allow them to achieve their final size. In addition, these systems are all considered to be nano-technology as defined by convention and multiple regulatory agencies (less than 100 nm), giving rise to regulatory issues. There are growing health and safety concerns about the application of nano-technology in foods.
Conventional food processing employs a wide range of physical and chemical treatments of foods. For example, conventional processing of red meats includes the following methods and devices used: (1) brine injection, which is injecting brine into muscle tissue with pointed needles, where the brine is water containing dissolved salt and curing substances, as well as additives such as phosphates, spices, sugar, carrageenan and soy proteins; (2) tumbling and massaging, which employ a rotating drum (tumbler) that slowly moves the meat inside, and which can include steel paddles inside to produce a mechanical massaging effect on the meat; (3) vacuum packaging, in which the meat is placed into a vacuum bag, air is removed from the bag, and the vacuum bag is sealed, either with or without gas flushing by injecting gas mixtures that inhibit bacterial growth after removing the air; (4) mixing and blending, in which the meat product and spices are blended in a mixer having a vessel with a rectangular or round bottom and two parallel shafts with paddles that mechanically mix the meat; and (5) emulsification, for fine meat emulsions, in which an emulsifier having a perforated plate is attached to a rotor blade, and a centrifugal pump forces the pre-ground meat through the perforated plate.
Since many foods, especially protein-based foods such as meats, poultry and fish, contain a large percentage of water, a hydrophobic agent applied on or into a protein-based food generally will not diffuse into the food quickly or evenly, since the hydrophobic agent does not readily mix with the water phase in the food. Adding a sufficient amount of a surfactant, such as an emulsifier, can allow a hydrophobic agent to disperse stably in a water phase; however, the addition of surfactants increases costs, and can affect the texture and the taste of the food.
Freezer burn, which can affect nearly any type of food, is another problem that affects the quality, taste, and texture of the food, decreases consumer appeal, and causes loss of economic value. For example, red meats, pork, poultry and fish, can develop freezer burn that appears as spots on the food surface where the food has become dehydrated. The primary mechanism of freezer burn is sublimation. When food is frozen, water molecules in the food form ice crystals. If the air that is adjacent to these ice crystals is cold enough and dry enough, the water molecules that formed the ice crystals in the food escape directly into the air by the process of sublimation. This dehydrates the food, causing the food to dry, shrivel, and appear “burned” at the spot. Freezer burn can also impart an unpleasant flavor and texture to the food, further decreasing consumer appeal, and value.
Thus, what are needed are submicron dispersions of hydrophobic agent particles that are substantially surfactant-free. What are further needed are submicron dispersions with an average particle size larger than 100 nm in diameter. What are additionally needed are dispersions that remain stable when diluted in aqueous fluid, which can be more flexibly employed in a food preparation process. What is needed is a dispersion concentrate that can be used in the same manner in a laboratory preparation, by an end user, or in a commercially-scaled preparation. What is needed is a dispersion concentrate that can be readily used in a beverage. What are needed are submicron dispersions of hydrophobic agent particles that are reproducible, and reproducibly employed if formed from a given mixture of hydrophobic agent(s) to a certain particle size specification. What are further needed are dispersions that can be made with at most limited heating. What is needed are foods combined with a submicron dispersion of hydrophobic agent, including those having improved texture, taste, nutritional value, odor, appearance, ease of preparation, and/or cost of production. Also needed is a dispersion that can be applied into or onto a food to prevent freezer burn.